1. Field of the Invention
The present invention relates to image modules and more particularly, to a wafer level image module, the method for making the same and the apparatus for assembling and testing the same.
2. Description of the Related Art
FIG. 12 shows a conventional CMOS (Complementary Metal-Oxide Semiconductor) image module 80. According to this design, the CMOS image module 80 comprises a sensor chip 82 and a lens holder 81 covering the sensor chip 82. The lens holder 81 comprises a rotary lens barrel 83, and a lens set 84 on the center of the rotary lens barrel 83. When the lens set 84 is mapping an image onto the sensor chip 82, the rotary lens barrel 83 is rotatable to change the distance between the lens set 84 and the sensor chip 82, thereby focusing light rays on the sensor chip 82.
FIG. 13 shows an image module according to WO2004/027880. This design of image module comprises an image pickup device 103 and a set of lenses 111 and 127. The lenses 111 and 127 are arranged in a stack and closely attached to the image pickup device 103 to map the image of incident light rays onto the image pickup device 103. The main feature of this patent is that the image pickup device 103 and the lenses 111 and 127 are made through an integrated circuit manufacturing process to minimize the size for use in a cell phone, PDA, or any of a variety of other consumer electronics.
However, during the fabrication of the image module according to WO2004/027880, the lenses 111 and 127 may deform by the manufacturing process and the manufacturing temperature. The focal distance of the finished product shows a 0-50 μm error when compared to the original theoretical design. In actual practice, the lenses 111 and 127 cannot accurately focus the image of incident light rays onto the image pickup device 103, resulting in an out-of-focus problem (see the imaginary line A or B in FIG. 13). Further, when mounting the lenses 111 and 127 on the image pickup device 103, the respective size tolerance, for example, 0-20 μm thickness tolerance of each glass chip makes distance control between the lenses 111 and 127 and the image pickup device 103 difficult, resulting in inaccurate focusing of the lenses 111 and 127 on the image pickup device 103.